REPUBLIC, Mo. (AP) — Police have seized five guns and two books from a 13-year-old boy officers allege had threatened a school shooting outside Springfield.

The Springfield News-Leader reports that police arrested an unidentified teenager in the Friday threat, alleging the boy said on social media that he would shoot up a Republic school with an AK-47.

A search warrant authorized police to seize “any writings, documents, journals” that could contain “data, writings or searches” associated with making a terrorist threat.

Court documents say the seized books were “American Sniper” and “The Darkest Path.” The former is about a soldier who recorded the most career sniper kills in U.S. military history. The latter is a fiction book about an ex-child soldier living in what the author’s website says is the “Second American Civil War.”